You successfully established a BGP session with a peer but do not see any routes learned. What could be causing this issue?

The situation where a BGP session is established with a peer yet no routes are learned can indeed be attributed to a routing policy blocking the routes. In BGP, policies are used to control which routes are advertised and accepted. If there is a policy in place that restricts the acceptance of routes from that specific peer, it can prevent any routes from being learned, even if the session is up and running. This makes the routing policy a critical component in BGP operations, as it determines the route filtering and can lead to this issue if misconfigured.

While it's true that an unreachable BGP peer could disrupt route learning, in this case, the session has reportedly been established, which indicates that reachability is confirmed. Similarly, if the BGP configuration were corrupted, it would likely result in a failure to establish the session altogether rather than simply no routes being learned. Lastly, if BGP were not enabled on the interface, the session itself would not be established, contradicting the premise of the question. Thus, the presence of an active session but lack of route learning points strongly to a filtering issue due to the routing policy.